Fire insurance, as you have discovered, is a complete ripoff. Most people pay fire insurance all their lives with no benefit whatsoever, and those such as yourself who are lucky enough to get a payout find that it is completely insufficient to replace their loss. I once computed the actual beneficial net present financial value of my fire insurance policy and it came out to $40 per month. The cost was $800 per month. That is typical. Homeowners pay $500 to $800 per year for something that is worth $30 to $50 per year. Ironically banks would actually make more money from mortgages if they did not require mortgagees to buy insurance, but nevertheless they insist on it. It is not about logic, but about fear and irrationality.
When I paid off my mortgage and gained ownership of my home the first thing I did was cancel my fire insurance. I now invest the money I would have wasted on insurance, making money instead of losing it. Being compelled to throw money down the toilet on fire insurance is one of the hidden costs of a homeowners mortgage in the United States.
In your situation, the main option is to borrow the money to rebuild the house using the land as collateral, if the land is valuable enough. Of course, you still owe the money for your original mortgage on your now (non-existent) home. So, to get a home, you will have to have the income to service two mortgages. A loan officer at a reputable bank can tell you whether you have the income necessary to support two mortgages.
If you were maxed out on your original mortgage, then you may not have enough income and you are screwed. In that case you will have to go back to renting and gradually paying off your old mortgage.
(If it were me, I would sue the insurance company pro se as a way to get the necessary money to rebuild the home, because insurance companies roll over like a $20 hooker when they get sued. Juries hate insurance companies. But I am unusual in that I love courtrooms and suing people. Most people are terrified of courtrooms though, so it may not be an option for you.)